WO2012020600A1 - Soundwave source and ultrasound generation device - Google Patents

Soundwave source and ultrasound generation device Download PDF

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Publication number
WO2012020600A1
WO2012020600A1 PCT/JP2011/063765 JP2011063765W WO2012020600A1 WO 2012020600 A1 WO2012020600 A1 WO 2012020600A1 JP 2011063765 W JP2011063765 W JP 2011063765W WO 2012020600 A1 WO2012020600 A1 WO 2012020600A1
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thick film
source
film conductor
sound
insulating substrate
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PCT/JP2011/063765
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French (fr)
Japanese (ja)
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浅田隆昭
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株式会社村田製作所
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K9/00—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers
    • G10K9/12—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers electrically operated

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  • the present invention relates to a sound wave source that generates a pressure wave by heating air and an ultrasonic wave generator provided with the sound wave source.
  • ultrasonic sonar is being studied as a candidate for object detection or non-contact input devices.
  • it is generally necessary to expand the frequency band of ultrasonic waves and increase the time resolution.
  • Patent Documents 1 and 2 disclose an apparatus that includes a heating element that generates heat when energized and generates air pressure waves by air heating by the heating element.
  • a heat insulating layer of SiO 2 is provided on an alumina substrate, a heat generating layer of Ta 2 N is formed thereon, a gold electrode layer is further deposited, and an aluminum heat sink is formed on the back surface of the substrate.
  • a device is shown which has been bonded.
  • Patent Document 2 discloses a sound wave source in which a thermal insulating layer made of porous silicon is provided on a silicon substrate, and a heating element thin film made of a resistive thin film is provided on the thermal insulating layer.
  • FIG. 1 is a cross-sectional view of the pressure wave generator of Patent Document 2.
  • This pressure wave generator includes a silicon substrate 1, a thermal insulating layer 2 such as porous silicon (Po-Si) or a polymer material film formed on the substrate 1, aluminum deposited on the thermal insulating layer 2, and the like.
  • the heating element thin film 3 and a signal terminal connected to each end of the heating element thin film 3 are provided.
  • the heating element thin film 3 is composed of an electric resistor that generates Joule heat or a Peltier element that generates and absorbs heat by the Peltier effect, and a driving voltage is applied via a signal terminal.
  • This drive voltage is a combination of an alternating current component and a direct current component so as to have either a positive or negative polarity.
  • a sound wave source that generates air pressure waves by heating air with a heating element (hereinafter referred to as a “thermally induced sound wave source”) is that the Joule heat of the conductor caused by the current directly heats and expands the air in the vicinity of the conductor.
  • the generation principle Since the heating element itself does not vibrate mechanically, it has no flat resonance and flat frequency characteristics.
  • a heat generating element with a small heat capacity heat insulation means capable of maintaining the temperature of the heat generating element for the same time as the period of the sound wave, and DC heat
  • a substrate having high thermal conductivity (heat dissipation means) for dissipating is required as a main component.
  • the heating element is a thin film electrode such as tantalum nitride or aluminum
  • the heat insulating means is an SiO 2 or porous silicon layer provided on the silicon substrate
  • the heat radiating means is an alumina substrate as a substrate.
  • silicon wafers As described above, both of the sound wave sources shown in Patent Documents 1 and 2 need to form a heating element thin film by a thin film process.
  • the surface of a silicon wafer is likely to be oxidized, and the heat insulating property may be deteriorated. In this case, heat to be converted into sound waves is easily radiated, and high sound pressure cannot be obtained. Also, a very expensive capital investment is required to perform the thin film process.
  • An object of the present invention is to provide a sound source and an ultrasonic generator that can be easily manufactured without using a thin film process or the like and can generate sound waves that have excellent heat insulation and can be used practically.
  • the acoustic wave source of the present invention is composed of an insulating substrate and a thick film conductor (electrode film or resistance film) formed on the insulating substrate and containing a metal material and a glass component.
  • the insulating substrate acts as a heat radiating means
  • the thick film conductor acts as a heat generating means
  • the glass component contained in the thick film conductive paste acts as a heat insulating means
  • the heat generating portion is near the interface of the insulating substrate. It is presumed to function as a heat insulating layer.
  • the thick film conductor is preferably formed by applying, printing and baking a conductive paste containing a metal material and a glass component on the insulating substrate.
  • An ultrasonic generator includes an insulating substrate and a sound source formed on the insulating substrate by a thick film conductor formed by printing and baking a thick film conductive paste containing a metal material and a glass component. And a burst wave voltage generation circuit for generating a burst wave voltage to be applied to the thick film conductor.
  • a sound wave source is formed only by forming a thick film conductor on an insulating substrate, it can be easily formed without using a thin film process or the like, and it can be used practically with excellent heat insulation.
  • a sound source and an ultrasonic generator capable of generating sound waves are obtained.
  • FIG. 1 is a cross-sectional view of a sound wave source disclosed in Patent Document 2.
  • 2A is a cross-sectional view of the sound source 101 according to the first embodiment
  • FIG. 2B is a plan view of the sound source 101.
  • FIG. 3 is a block diagram of the ultrasonic generator 201 provided with the sound wave source 101 and its characteristic measuring device 301.
  • FIG. 4 shows waveforms of ultrasonic waves measured by the ultrasonic generator 201 and the characteristic measuring device 301 shown in FIG.
  • FIG. 5 is a plan view of the sound wave source 102 according to the second embodiment.
  • FIG. 6 shows the result of measuring the sound pressure for each frequency by changing the frequency of the pulse waveform.
  • FIG. 7A shows a time waveform of an impulse response
  • FIG. 7B shows a frequency spectrum.
  • FIG. 8 shows the measurement result of the sound pressure with respect to the drive voltage.
  • FIG. 9 is a diagram showing propagation characteristics, where the horizontal axis represents distance and the vertical axis represents sound pressure.
  • FIG. 10 is a diagram showing the directivity characteristics, where the horizontal axis represents the azimuth and the vertical axis represents the decibel value of the sound pressure.
  • FIG. 11 is a plan view of three sound wave sources according to the third embodiment.
  • FIG. 12 is a circuit diagram of the ultrasonic generator 204 according to the fourth embodiment.
  • FIG. 13 shows an example of the sound pressure waveform of the sound wave radiated from the gate signal of the MOSFET 42 generated by the pulse generation circuit 41 shown in FIG.
  • FIG. 2A is a cross-sectional view of the sound source 101 according to the first embodiment
  • FIG. 2B is a plan view of the sound source 101.
  • the sound wave source 101 includes an insulating substrate 11 and a thick film conductor 13 formed on the insulating substrate 11 and containing a metal material and a glass component. Furthermore, connection electrodes 14 and 15 that are electrically connected to both ends of the thick film conductor 13 are provided on the insulating substrate 11.
  • the thick film conductor 13 is, for example, a conductor film or a resistance film made of a conductor such as Ag, Ag / Pd, Pt, RuO 2 and a glass component.
  • the conductive components of the thick film conductive paste used when forming the thick film conductor 13 are Pd, Ag, Pt and RuO 2 , and contain about 20-30 wt% of glass.
  • the thick film conductor 13 is preferably formed on the insulating substrate 11 by applying, printing and baking a conductor paste containing a metal material and a glass component. It can be easily manufactured by a thick film process.
  • connection electrodes 14 and 15 may be Ag, AgPd, or the like, or a thick film electrode such as Sn, Al, or Cu, or a thin film electrode formed by sputtering or vapor deposition. Any conductor may be used as long as it is obtained.
  • this thick film conductor contains a metal material and a glass component, the metal material substantially functions as a heat generating member, and this glass component performs a heat insulating action. Further, since the thick film conductor material is baked on the substrate, it is expected that the thick film conductor itself in the vicinity of the interface with the substrate functions as a heat insulator of the heat generation portion by the thick film conductor other than the interface. For this reason, the dedicated heat insulation means as shown in Patent Documents 1 and 2 is not necessary as a component.
  • the thick film conductor of the present invention is a thick film, it is less susceptible to oxidation than a thin film, and the glass component is contained in the thick film conductor, so that the surface of the thick film conductor is less likely to be oxidized. Arise. Furthermore, since it can be manufactured by a thick film process, it can be manufactured easily.
  • FIG. 3 is a block diagram of an ultrasonic generator 201 including the sound source 101 and a characteristic measuring device 301 thereof.
  • the ultrasonic generator 201 includes a sound wave source 101, a burst wave signal generation circuit 21, and a power amplification circuit 22.
  • the burst wave signal generation circuit 21 and the power amplification circuit 22 constitute a “burst wave voltage generation circuit” according to the present invention.
  • the characteristic measuring device 301 includes a microphone 31, a preamplifier 32, a band pass filter 33 and an oscilloscope 34.
  • FIG. 4 shows an ultrasonic waveform measured by the ultrasonic generator 201 and the characteristic measuring device 301 shown in FIG. 4A shows the driving voltage waveform of the sound wave source 101, and FIG. 4B shows the sound pressure waveform of the ultrasonic wave received by the microphone 31.
  • FIG. 4A shows the driving voltage waveform of the sound wave source 101
  • FIG. 4B shows the sound pressure waveform of the ultrasonic wave received by the microphone 31.
  • a sound wave source having a structure shown in FIG. 5 was used as the sound wave source 102.
  • a thick film conductive paste containing 55 wt% of AgPd as a main component, 25 wt% of a Ru-Si glass component, and 20 wt% of a binder and a solvent component is folded on the surface of the alumina insulating substrate 11.
  • the thick film electrode 13 was formed by printing on the shape and baking. Further, connection electrodes 14 and 15 made of Ag were formed by sputtering on both ends of the thick film electrode.
  • the thick film electrode 13 has a total length of 12 mm ⁇ width of 1 mm ⁇ thickness of 20 ⁇ m and is folded back at a portion of about 6 mm.
  • the room temperature resistance value (25 ° C.) of the acoustic wave source 102 is 10 ⁇ , and the thick film electrode 13 portion is exposed on the surface.
  • the microphone 31 is a 1/4 inch condenser microphone.
  • the pass band of the band pass filter is 3 to 80 kHz.
  • the sound wave source 101 and the microphone 31 were placed 5 cm apart.
  • the drive voltage waveform is a sinusoidal pulse for two cycles, but as shown in FIG. . It can be seen that the center frequency of the pulse waveform is 20 kHz, while the drive signal is 20 kHz, while the sound pressure is doubled by 40 kHz. This is because heat generation occurs regardless of whether the voltage (current) is positive or negative.
  • FIG. 6 shows the result of measuring the sound pressure for each frequency by changing the frequency of the pulse waveform.
  • the frequency of the drive signal is about 16 kHz, that is, the sound pressure frequency
  • the sound pressure reaches a peak at about 32 kHz.
  • the Q value sound pressure peak frequency ⁇ ⁇ (the higher frequency among the frequencies at which the sound pressure is halved) ⁇ (sound pressure is 1 ⁇ 2) from the obtained frequency. ) ⁇
  • the frequency is as low as about 1.2, which indicates that it is not a resonance type sound source.
  • the reason why the sensitivity lowers in the low frequency range than in the high frequency range from the peak frequency is considered to be because the time constant of the heat insulation effect is small.
  • the sensitivity in the low frequency region will be improved if the heat insulation effect is improved.
  • the sensitivity fall in a high frequency region originates in the heat capacity of a thick film conductor, this is also expected to be improved by reducing the heat capacity of the thick film conductor.
  • FIG. 7A is a time waveform of sound pressure when driven by an impulse current having a width of 15 ⁇ sec in FIG. 6, and FIG. 7B is an FFT spectrum thereof.
  • the sound pressure waveform is a short pulse of almost one cycle, and it can be visually understood that high time resolution can be obtained.
  • the peak of the spectrum is about 25 kHz, the effective Q value is about 0.8, and the frequency characteristic obtained by the impulse method is almost similar to the tendency of the frequency characteristic shown in FIG.
  • FIG. 8 shows the measurement result of the sound pressure with respect to the drive voltage.
  • the horizontal axis is the drive voltage
  • the vertical axis is the sound pressure. It can be confirmed that the sound pressure increases in proportion to the square of the drive voltage.
  • the piezoelectric method and the electromagnetic method can obtain a sound pressure output proportional to the driving voltage or driving current, but are different in this respect and have a relationship similar to the electrostriction method.
  • the driving voltage of 100Vp-p the peak power is 250W and the effective power in the burst wave is 125W. Since it is a pulse drive, it can be reduced to 1.25W at a duty of 1%, for example, and it becomes a practical power level.
  • the reason why the sound pressure is saturated at a drive voltage of 180 Vp-p or more is that the output of the power amplifier used in this experiment is saturated.
  • FIG. 9 is a diagram showing propagation characteristics, where the horizontal axis represents the distance from the sound wave source to the microphone, and the vertical axis represents the sound pressure. From FIG. 9, it can be confirmed that the sound pressure is diffused and attenuated in inverse proportion to the distance. Since the sound pressure is about 3Pap-p at a distance of 3cm, it can be used for object detection at a short distance. For example, it can be used for applications such as copier and printer paper double feed detection.
  • FIG. 10 is a diagram showing the directivity, where the horizontal axis represents the azimuth angle and the vertical axis represents the relative value of the sound pressure.
  • the half angle is about 70 degrees (-35 ° to 35 °) when the angle at which the sound pressure reaches the maximum is 0 ° C. From FIG. 6, it is found that the directivity is sufficiently narrow considering that the frequency is 32 kHz and the length of the transmission surface is about 6 mm because it is a folded electrode.
  • an ultrasonic sensor using a piezoelectric element attached to the bottom surface of a bottomed cylindrical case and utilizing bending vibration by the piezoelectric element is known to obtain a narrow directivity as the frequency increases.
  • the 11 includes an insulating substrate 11, a thick film conductor 13 including a metal material and a glass component, and connection electrodes 14 and 15 formed on the insulating substrate 11. .
  • a meander line pattern is formed in a circular region as indicated by a broken-line circle.
  • the thick film conductor 13 shown in FIG. 11B forms a meander line pattern in a substantially square region.
  • the thick film conductor 13 shown in FIG. 11C also has a substantially square shape as a whole, but a plurality of lines are connected in parallel.
  • the directivity can be controlled and designed by the area and shape of the formation region of the thick film conductor 13. For example, as shown in FIGS. 11 (A) to 11 (C), as the area of the thick film conductor 13 is increased, the area in which the isophase planes of sound waves are parallel increases, so that the width of the directional beam is increased. Since it can narrow, it is more preferable. Further, if the shape of the region where the thick film conductor 13 is formed has different vertical and horizontal widths, the vertical and horizontal widths of the beam can be made different.
  • the thick film conductor 13 may be determined in accordance with the required resistance value, area, and shape.
  • the resistance value is also determined by the film thickness of the thick film conductor 13, but since the film thickness and the heat capacity are closely related, when driving with a high-frequency driving voltage, the resistance is made thin enough to obtain a predetermined sensitivity. Various adjustments are preferable.
  • the thick film conductor of the present invention is formed by applying, printing and baking a conductor paste containing a metal material and a glass component on an alumina substrate, so that the resistance value, area, shape, etc. can be easily adjusted. It can be carried out.
  • the wave transmission surface can be freely set, and directivity control and design are facilitated.
  • FIG. 12 is a circuit diagram of the ultrasonic generator 204 according to the fourth embodiment.
  • the ultrasonic generator 204 includes a pulse generation circuit 41, a DC power supply 43, a MOSFET 42, and a sound wave source 104.
  • the source of the MOSFET 42 is grounded
  • the sound wave source 104 is connected between the drain of the MOSFET 42 and the DC power supply 43
  • the pulse voltage of the pulse generating circuit 41 is applied between the gate and source of the MOSFET 42.
  • FIG. 13 shows an example of the gate signal of the MOSFET 42 generated by the pulse generation circuit 41 shown in FIG. 12 and the sound pressure waveform of the sound wave radiated from the sound wave source 104 (the waveform of the signal detected by the microphone).
  • the left waveform in FIG. 13 is a gate signal
  • the right waveform is a sound pressure waveform.
  • One pulse width of the gate signal is 12.5 ⁇ s, and an example of one wave, two waves, and four waves from the top is shown. According to this configuration, since the drive current exists in a single pole, a sound pressure waveform having the same wave number as the gate signal can be obtained.
  • the thick film conductor surface of the insulating substrate may be formed in a curved surface.
  • the equiphase surface of the pressure wave of air generated by air heating is formed along the curved surface of the thick film conductor surface. Therefore, the beam shape of the sound wave may be controlled by determining the curved surface shape of the thick film conductor surface of the insulating substrate.
  • the thick film conductor pattern is constituted by an aggregate pattern of a plurality of patterns, and the burst wave voltage generating circuit applies burst wave voltages having different phases to the plurality of thick film conductor patterns. May be. Thereby, the directivity direction of the ultrasonic wave with respect to the substrate can be controlled.
  • the thick film conductor of the present invention has a structure including a metal material and a glass component, it can function not only as a heating member but also as an electrode. For this reason, a connection electrode is not necessarily required.

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Abstract

A soundwave source (101) is provided with an insulating substrate (11) and a thick film conductor (13) which is formed on the insulating substrate (11) and includes a metal material and a glass component. In addition, the soundwave source (101) is provided with connection electrodes (14, 15) which are arranged on the insulating substrate (11) and electrically conduct with both ends of the thick film conductor (13). Since a glass component is included in thick film conductive material of the thick film conductor (13), this glass component presents a thermal insulation effect. By means of this construction, a soundwave source and ultrasound generation device can be constructed which are capable of generating sound waves, can be supplied for practical use, have excellent thermal insulation properties, and can easily be formed without requiring the use of a thin-film process etc.

Description

音波源および超音波発生装置Sonic source and ultrasonic generator
　本発明は、空気を加熱することによって圧力波を発生させる音波源およびそれを備えた超音波発生装置に関する。 The present invention relates to a sound wave source that generates a pressure wave by heating air and an ultrasonic wave generator provided with the sound wave source.
　物体検知あるいは非接触型の入力デバイスの候補として、超音波ソーナーの利用が検討されている。空間において対象物までの距離を検知するためには、一般に超音波の周波数帯域を拡大し、時間分解能を上げる必要がある。 The use of ultrasonic sonar is being studied as a candidate for object detection or non-contact input devices. In order to detect the distance to an object in space, it is generally necessary to expand the frequency band of ultrasonic waves and increase the time resolution.
　医療用の超音波診断装置などに用いられる超音波トランスデューサにおいては、生体など対象とする媒質の音響インピーダンスが水にほぼ等しいため、音波発生素子とのインピーダンス整合が良く、エネルギー伝送効率も高い。このため、バッキング材の音響インピーダンスを圧電素子のそれと近い値として振動をダンピングし、Ｑを下げることが容易である。また、圧電音波発生素子とバッキング材とのインピーダンスを同一にすれば、完全な非共振型の音源を得ることが可能である。 In an ultrasonic transducer used in a medical ultrasonic diagnostic apparatus or the like, since the acoustic impedance of a target medium such as a living body is almost equal to water, impedance matching with a sound wave generating element is good and energy transmission efficiency is high. For this reason, it is easy to damp vibration and lower Q by setting the acoustic impedance of the backing material to a value close to that of the piezoelectric element. Further, if the impedances of the piezoelectric acoustic wave generating element and the backing material are the same, a complete non-resonant type sound source can be obtained.
　一方、空気中においては媒質のインピーダンスが極端に低いため、実用に供する放射音圧感度を得るためには、圧電体とそれを用いた振動系の共振を利用し、大きな機械的変位を実現する必要がある。このため原理的にＱは高く、帯域を拡げるために振動をダンピングすると音圧が著しく低下してしまう。このため、非共振型で実用的な超音波音源はこれまで存在しなかった。 On the other hand, since the impedance of the medium is extremely low in the air, in order to obtain radiated sound pressure sensitivity for practical use, a large mechanical displacement is realized using the resonance of the piezoelectric body and the vibration system using it. There is a need. Therefore, in principle, Q is high, and if the vibration is damped in order to widen the band, the sound pressure is significantly reduced. For this reason, there has been no non-resonant and practical ultrasonic sound source.
　通電によって発熱する発熱体を備え、この発熱体による空気加熱によって空気の圧力波を発生する装置は例えば特許文献１，２に示されている。特許文献１には、アルミナ基板の上にSiO2の断熱層を設け、さらにその上にTa2Nの発熱層を形成し、さらに金の電極層を蒸着し、基板の裏面にアルミニウムの放熱板を接着した装置が示されている。特許文献２には、シリコン基板上にポーラスシリコンからなる熱絶縁層が設けられ、この熱絶縁層上に抵抗薄膜からなる発熱体薄膜が設けられた音波源が示されている。 For example, Patent Documents 1 and 2 disclose an apparatus that includes a heating element that generates heat when energized and generates air pressure waves by air heating by the heating element. In Patent Document 1, a heat insulating layer of SiO 2 is provided on an alumina substrate, a heat generating layer of Ta 2 N is formed thereon, a gold electrode layer is further deposited, and an aluminum heat sink is formed on the back surface of the substrate. A device is shown which has been bonded. Patent Document 2 discloses a sound wave source in which a thermal insulating layer made of porous silicon is provided on a silicon substrate, and a heating element thin film made of a resistive thin film is provided on the thermal insulating layer.
　図１は特許文献２の圧力波発生装置の断面図である。この圧力波発生装置は、シリコン基板１、基板１上に形成されたポーラスシリコン（Ｐｏ－Ｓｉ）や高分子材料膜などの熱絶縁層２、熱絶縁層２上に被着されたアルミニウムなどの発熱体薄膜３、発熱体薄膜３の各端部に接続された信号端子を備えている。発熱体薄膜３は、ジュール熱を発生する電気抵抗体あるいはペルチエ効果による発熱／吸熱を行うペルチエ素子で構成され、信号端子を介して駆動電圧が印加される。この駆動電圧は正負いずれか一方の極性となるように、交流成分と直流成分とが合成されたものである。 FIG. 1 is a cross-sectional view of the pressure wave generator of Patent Document 2. This pressure wave generator includes a silicon substrate 1, a thermal insulating layer 2 such as porous silicon (Po-Si) or a polymer material film formed on the substrate 1, aluminum deposited on the thermal insulating layer 2, and the like. The heating element thin film 3 and a signal terminal connected to each end of the heating element thin film 3 are provided. The heating element thin film 3 is composed of an electric resistor that generates Joule heat or a Peltier element that generates and absorbs heat by the Peltier effect, and a driving voltage is applied via a signal terminal. This drive voltage is a combination of an alternating current component and a direct current component so as to have either a positive or negative polarity.
特開平３－１４０１００号公報Japanese Patent Laid-Open No. 3-140100 特開平１１－３００２７４号公報Japanese Patent Application Laid-Open No. 11-300274
　発熱体による空気加熱によって空気の圧力波を発生する音波源（以下、「熱誘起型音波源」という。）は、電流による導体のジュール熱が導体近傍の空気を直接加熱膨張させることをその音波発生原理としている。発熱体自体は機械的に振動しないため、共振がなくフラットな周波数特性を持つ。 A sound wave source that generates air pressure waves by heating air with a heating element (hereinafter referred to as a “thermally induced sound wave source”) is that the Joule heat of the conductor caused by the current directly heats and expands the air in the vicinity of the conductor. The generation principle. Since the heating element itself does not vibrate mechanically, it has no flat resonance and flat frequency characteristics.
　熱誘起型音波源としての機能を発現するためには、熱容量の小さな発熱体と、音波の周期と同程度の時間のあいだ、発熱体の温度を保持可能な断熱手段、そして直流的な熱を放散するための熱伝導率の高い基板（放熱手段）が主な構成要素として必要である。 In order to realize the function as a heat-induced acoustic wave source, a heat generating element with a small heat capacity, heat insulation means capable of maintaining the temperature of the heat generating element for the same time as the period of the sound wave, and DC heat A substrate having high thermal conductivity (heat dissipation means) for dissipating is required as a main component.
　特許文献１，２で提案されている構成では、発熱体は窒化タンタルやアルミニウムなどの薄膜電極、断熱手段はシリコン基板上に設けられたSiO2やポーラスシリコン層、放熱手段は基板としてのアルミナ基板やシリコンウエハである。このように、特許文献１，２に示されている音波源はいずれも薄膜プロセスによって発熱体薄膜を形成する必要があるが、特許文献１，２のような薄膜プロセスによって形成されたアルミナ基板やシリコンウエハでは表面が酸化されやすく、断熱性が劣化するおそれがある。この場合、音波に変換されるべき熱が放熱されやすくなり、高い音圧が得られない。また、薄膜プロセスを行うためには非常に高額な設備投資を要する。 In the configurations proposed in Patent Documents 1 and 2, the heating element is a thin film electrode such as tantalum nitride or aluminum, the heat insulating means is an SiO 2 or porous silicon layer provided on the silicon substrate, and the heat radiating means is an alumina substrate as a substrate. And silicon wafers. As described above, both of the sound wave sources shown in Patent Documents 1 and 2 need to form a heating element thin film by a thin film process. The surface of a silicon wafer is likely to be oxidized, and the heat insulating property may be deteriorated. In this case, heat to be converted into sound waves is easily radiated, and high sound pressure cannot be obtained. Also, a very expensive capital investment is required to perform the thin film process.
　本発明は、薄膜プロセス等を用いずとも容易に製造できるとともに、断熱性に優れ実用に供し得る音波が発生可能な音波源および超音波発生装置を提供することを目的としている。 An object of the present invention is to provide a sound source and an ultrasonic generator that can be easily manufactured without using a thin film process or the like and can generate sound waves that have excellent heat insulation and can be used practically.
　本発明の音波源は、絶縁性基板と、この絶縁性基板上に形成された、金属材料とガラス成分を含む厚膜導体（電極膜または抵抗膜）とで構成されたものである。 The acoustic wave source of the present invention is composed of an insulating substrate and a thick film conductor (electrode film or resistance film) formed on the insulating substrate and containing a metal material and a glass component.
　この構造により、絶縁性基板は放熱手段として作用し、厚膜導体は発熱手段として作用し、厚膜導電ペーストに含まれるガラス成分は断熱手段として作用し、絶縁性基板の界面付近で発熱部分の断熱層として機能するものと推測される。 With this structure, the insulating substrate acts as a heat radiating means, the thick film conductor acts as a heat generating means, the glass component contained in the thick film conductive paste acts as a heat insulating means, and the heat generating portion is near the interface of the insulating substrate. It is presumed to function as a heat insulating layer.
　また、前記厚膜導体は、前記絶縁性基板上に、金属材料とガラス成分とを含む導体ペーストを塗布・印刷し焼き付けることによって形成されたものであることが好ましい。 The thick film conductor is preferably formed by applying, printing and baking a conductive paste containing a metal material and a glass component on the insulating substrate.
　本発明の超音波発生装置は、絶縁性基板と、この絶縁性基板上に形成された、金属材料とガラス成分を含む厚膜導電ペーストの印刷および焼き付けによる厚膜導体とで構成された音波源と、前記厚膜導体に印加するバースト波電圧を発生するバースト波電圧発生回路と、を備える。 An ultrasonic generator according to the present invention includes an insulating substrate and a sound source formed on the insulating substrate by a thick film conductor formed by printing and baking a thick film conductive paste containing a metal material and a glass component. And a burst wave voltage generation circuit for generating a burst wave voltage to be applied to the thick film conductor.
　本発明によれば、絶縁性基板に厚膜導体を形成するだけで音波源が構成されるので、薄膜プロセス等を用いる必要がなく容易に形成することができ、断熱性に優れ実用に供し得る音波が発生可能な音波源および超音波発生装置が得られる。 According to the present invention, since a sound wave source is formed only by forming a thick film conductor on an insulating substrate, it can be easily formed without using a thin film process or the like, and it can be used practically with excellent heat insulation. A sound source and an ultrasonic generator capable of generating sound waves are obtained.
図１は特許文献２の音波源の断面図である。FIG. 1 is a cross-sectional view of a sound wave source disclosed in Patent Document 2. 図２（Ａ）は第１の実施形態に係る音波源１０１の断面図、図２（Ｂ）は音波源１０１の平面図である。2A is a cross-sectional view of the sound source 101 according to the first embodiment, and FIG. 2B is a plan view of the sound source 101. 図３は音波源１０１を備えた超音波発生装置２０１およびその特性測定装置３０１のブロック図である。FIG. 3 is a block diagram of the ultrasonic generator 201 provided with the sound wave source 101 and its characteristic measuring device 301. 図４は図３に示した超音波発生装置２０１および特性測定装置３０１で測定した超音波の波形である。FIG. 4 shows waveforms of ultrasonic waves measured by the ultrasonic generator 201 and the characteristic measuring device 301 shown in FIG. 図５は第２の実施形態に係る音波源１０２の平面図である。FIG. 5 is a plan view of the sound wave source 102 according to the second embodiment. 図６は、パルス波形の周波数を変化させて各周波数に対する音圧を測定した結果である。FIG. 6 shows the result of measuring the sound pressure for each frequency by changing the frequency of the pulse waveform. 図７（Ａ）はインパルス応答の時間波形、図７（Ｂ）は周波数スペクトルである。FIG. 7A shows a time waveform of an impulse response, and FIG. 7B shows a frequency spectrum. 図８は駆動電圧に対する音圧の測定結果である。FIG. 8 shows the measurement result of the sound pressure with respect to the drive voltage. 図９は伝搬特性を示す図であり、横軸は距離、縦軸は音圧である。FIG. 9 is a diagram showing propagation characteristics, where the horizontal axis represents distance and the vertical axis represents sound pressure. 図１０は指向特性を示す図であり、横軸は方位角、縦軸は音圧のデシベル値である。FIG. 10 is a diagram showing the directivity characteristics, where the horizontal axis represents the azimuth and the vertical axis represents the decibel value of the sound pressure. 図１１は第３の実施形態に係る３つの音波源の平面図である。FIG. 11 is a plan view of three sound wave sources according to the third embodiment. 図１２は第４の実施形態に係る超音波発生装置２０４の回路図である。FIG. 12 is a circuit diagram of the ultrasonic generator 204 according to the fourth embodiment. 図１３は、図１２に示したパルス発生回路４１により発生されるMOSFET４２のゲート信号と音波源１０４から放射される音波の音圧波形の例である。FIG. 13 shows an example of the sound pressure waveform of the sound wave radiated from the gate signal of the MOSFET 42 generated by the pulse generation circuit 41 shown in FIG.
《第１の実施形態》
　第１の実施形態に係る音波源および超音波発生装置について図２を参照して説明する。
　図２（Ａ）は第１の実施形態に係る音波源１０１の断面図、図２（Ｂ）は音波源１０１の平面図である。この音波源１０１は、絶縁性基板１１と、この絶縁性基板１１上に形成された、金属材料とガラス成分を含む厚膜導体１３を備えている。さらに、絶縁性基板１１上には厚膜導体１３の両端と電気的に導通する接続電極１４，１５を備えている。 << First Embodiment >>
A sound source and an ultrasonic generator according to the first embodiment will be described with reference to FIG.
2A is a cross-sectional view of the sound source 101 according to the first embodiment, and FIG. 2B is a plan view of the sound source 101. The sound wave source 101 includes an insulating substrate 11 and a thick film conductor 13 formed on the insulating substrate 11 and containing a metal material and a glass component. Furthermore, connection electrodes 14 and 15 that are electrically connected to both ends of the thick film conductor 13 are provided on the insulating substrate 11.
　絶縁性基板１１は例えばアルミナ基板等のセラミック基板や放熱性の優れたガラス基板等を用いることができる。厚膜導体１３は例えば、Ag,Ag/Pd,Pt,RuO2等の導電体とガラス成分からなる導体膜または抵抗膜である。この厚膜導体１３を形成する際に用いる厚膜導電ペーストの導電成分はPd、Ag、PtやRuO2であり、20-30wt%程度のガラスを含む。この厚膜導体１３は、絶縁性基板１１上に、金属材料とガラス成分とを含む導体ペーストを塗布・印刷し焼き付けることによって形成されることが好ましい。厚膜プロセスにより容易に製造することができる。また、接続電極１４，１５はAg，AgPd等、あるいはSn，Al, Cu等の厚膜電極またはスパッタや蒸着による薄膜電極等を用いてもよく、厚膜導体と外部との電気的な接続が得られれば如何なる導体でもよい。 As the insulating substrate 11, for example, a ceramic substrate such as an alumina substrate or a glass substrate having excellent heat dissipation can be used. The thick film conductor 13 is, for example, a conductor film or a resistance film made of a conductor such as Ag, Ag / Pd, Pt, RuO 2 and a glass component. The conductive components of the thick film conductive paste used when forming the thick film conductor 13 are Pd, Ag, Pt and RuO 2 , and contain about 20-30 wt% of glass. The thick film conductor 13 is preferably formed on the insulating substrate 11 by applying, printing and baking a conductor paste containing a metal material and a glass component. It can be easily manufactured by a thick film process. Further, the connection electrodes 14 and 15 may be Ag, AgPd, or the like, or a thick film electrode such as Sn, Al, or Cu, or a thin film electrode formed by sputtering or vapor deposition. Any conductor may be used as long as it is obtained.
　この厚膜導体は金属材料とガラス成分と含んでいるので、金属材料が実質的に発熱部材としての機能を果たし、このガラス成分が断熱作用を果たす。また、厚膜導体材料が基板に焼き付けられていることにより、基板との界面付近の厚膜導体自体が界面以外の厚膜導体による発熱部分の断熱体として機能することが予想される。このため、特許文献１，２に示されているような専用の断熱手段は構成要素として不要である。しかも本願発明の厚膜導体は、厚膜であるので薄膜に比べて酸化の影響を受けにくく、厚膜導体中にガラス成分が含まれることによって、厚膜導体の表面が酸化しにくくなる効果も生じる。さらに、厚膜プロセスで製造できるので、容易に製造できる。 Since this thick film conductor contains a metal material and a glass component, the metal material substantially functions as a heat generating member, and this glass component performs a heat insulating action. Further, since the thick film conductor material is baked on the substrate, it is expected that the thick film conductor itself in the vicinity of the interface with the substrate functions as a heat insulator of the heat generation portion by the thick film conductor other than the interface. For this reason, the dedicated heat insulation means as shown in Patent Documents 1 and 2 is not necessary as a component. In addition, since the thick film conductor of the present invention is a thick film, it is less susceptible to oxidation than a thin film, and the glass component is contained in the thick film conductor, so that the surface of the thick film conductor is less likely to be oxidized. Arise. Furthermore, since it can be manufactured by a thick film process, it can be manufactured easily.
《第２の実施形態》
　第２の実施形態に係る音波源および超音波発生装置について図３～図１０を参照して説明する。
　図３は前記音波源１０１を備えた超音波発生装置２０１およびその特性測定装置３０１のブロック図である。
　超音波発生装置２０１は、音波源１０１、バースト波信号発生回路２１および電力増幅回路２２を備えている。バースト波信号発生回路２１および電力増幅回路２２は本発明に係る「バースト波電圧発生回路」を構成している。
　特性測定装置３０１は、マイク３１、プリアンプ３２、バンドパスフィルタ３３およびオシロスコープ３４を備えている。 << Second Embodiment >>
A sound source and an ultrasonic generator according to a second embodiment will be described with reference to FIGS.
FIG. 3 is a block diagram of an ultrasonic generator 201 including the sound source 101 and a characteristic measuring device 301 thereof.
The ultrasonic generator 201 includes a sound wave source 101, a burst wave signal generation circuit 21, and a power amplification circuit 22. The burst wave signal generation circuit 21 and the power amplification circuit 22 constitute a “burst wave voltage generation circuit” according to the present invention.
The characteristic measuring device 301 includes a microphone 31, a preamplifier 32, a band pass filter 33 and an oscilloscope 34.
　図４は図３に示した超音波発生装置２０１および特性測定装置３０１で測定した超音波の波形である。図４（Ａ）は音波源１０１の駆動電圧波形、図４（Ｂ）はマイク３１で受けた超音波の音圧波形である。 FIG. 4 shows an ultrasonic waveform measured by the ultrasonic generator 201 and the characteristic measuring device 301 shown in FIG. 4A shows the driving voltage waveform of the sound wave source 101, and FIG. 4B shows the sound pressure waveform of the ultrasonic wave received by the microphone 31. FIG.
　ここで、音波源１０２は、図５に示される構造を有する音波源を用いた。具体的には、アルミナ絶縁性基板１１の表面に、主成分としてAgPdを55wt%、Ru-Si系のガラス成分を25wt%、バインダー及び溶剤成分が20wt%を含有した厚膜導電ペーストを、折り返し形状に印刷して焼き付けて厚膜電極１３を形成した。また、厚膜電極の両端部にはAgからなる接続電極１４，１５をスパッタで形成した。なお、厚膜電極１３は、全長１２ｍｍ×幅１ｍｍ×厚み２０μｍであり、約６ｍｍの部分で折れ返されている。この音波源１０２の室温抵抗値（２５℃）は１０Ωであり、厚膜電極１３部分を表面に露出している。 Here, a sound wave source having a structure shown in FIG. 5 was used as the sound wave source 102. Specifically, a thick film conductive paste containing 55 wt% of AgPd as a main component, 25 wt% of a Ru-Si glass component, and 20 wt% of a binder and a solvent component is folded on the surface of the alumina insulating substrate 11. The thick film electrode 13 was formed by printing on the shape and baking. Further, connection electrodes 14 and 15 made of Ag were formed by sputtering on both ends of the thick film electrode. The thick film electrode 13 has a total length of 12 mm × width of 1 mm × thickness of 20 μm and is folded back at a portion of about 6 mm. The room temperature resistance value (25 ° C.) of the acoustic wave source 102 is 10Ω, and the thick film electrode 13 portion is exposed on the surface.
　マイク３１は1/4インチのコンデンサマイクロホンである。バンドパスフィルタの通過帯域は３～８０ｋＨｚである。音波源１０１とマイク３１とは５ｃｍ離して両者を配置した。 The microphone 31 is a 1/4 inch condenser microphone. The pass band of the band pass filter is 3 to 80 kHz. The sound wave source 101 and the microphone 31 were placed 5 cm apart.
　図４（Ａ）に示すように、駆動電圧波形は2サイクル分の正弦波パルスであるが、図４（Ｂ）に表れているように、音圧波形はその倍の4サイクルが観測される。パルス波形の中心周波数は駆動信号が20kHzであるのに対して音圧においては40kHzと倍の周波数になっている様子が確認できる。発熱は電圧（電流）の正負に関わらず生じるためである。 As shown in FIG. 4A, the drive voltage waveform is a sinusoidal pulse for two cycles, but as shown in FIG. . It can be seen that the center frequency of the pulse waveform is 20 kHz, while the drive signal is 20 kHz, while the sound pressure is doubled by 40 kHz. This is because heat generation occurs regardless of whether the voltage (current) is positive or negative.
　図６は、パルス波形の周波数を変化させて各周波数に対する音圧を測定した結果である。駆動信号の周波数が約16kHz、すなわち音圧の周波数で表すと約32kHzで音圧はピークになっている。このようなピークが存在するが、得られた周波数からQ値（音圧のピーク周波数÷｛（音圧が１／２となる周波数のうち高い方の周波数）－（音圧が１／２となる周波数のうち低い方の周波数）　｝）を計算すると、約1.2と非常に低く、共振型音源ではないことが分かる。ピーク周波数より高周波域に比べて低周波域でより感度が低下する理由は、断熱効果の時定数が小さいためであると考えられる。したがって、アルミナ基板及び厚膜導体の形状・構造を調整することによって、断熱効果を上げれば低周波数域での感度も改善することが予想される。また、高周波域での感度低下は厚膜導体の熱容量に起因すると考えられるので、これも厚膜導体の熱容量の低減化によって改善するものと予想される。 FIG. 6 shows the result of measuring the sound pressure for each frequency by changing the frequency of the pulse waveform. When the frequency of the drive signal is about 16 kHz, that is, the sound pressure frequency, the sound pressure reaches a peak at about 32 kHz. Although such a peak exists, the Q value (sound pressure peak frequency ÷ {(the higher frequency among the frequencies at which the sound pressure is halved) −− (sound pressure is ½) from the obtained frequency. )}), The frequency is as low as about 1.2, which indicates that it is not a resonance type sound source. The reason why the sensitivity lowers in the low frequency range than in the high frequency range from the peak frequency is considered to be because the time constant of the heat insulation effect is small. Therefore, by adjusting the shape and structure of the alumina substrate and the thick film conductor, it is expected that the sensitivity in the low frequency region will be improved if the heat insulation effect is improved. Moreover, since it is thought that the sensitivity fall in a high frequency region originates in the heat capacity of a thick film conductor, this is also expected to be improved by reducing the heat capacity of the thick film conductor.
　図７（Ａ）は図６の幅１５μｓｅｃのインパルス電流で駆動した場合の音圧の時間波形、図７（Ｂ）はそのFFTスペクトルである。音圧波形はほぼ１周期分の短パルスとなっており、高い時間分解能を得られることが視覚的にも理解できる。スペクトルのピークは約25kHzであるが、実効的なQ値は0.8程度であり、インパルス法で求めた周波数特性についても、図６に示した周波数特性の傾向とほぼ相似な特性が得られた。 7A is a time waveform of sound pressure when driven by an impulse current having a width of 15 μsec in FIG. 6, and FIG. 7B is an FFT spectrum thereof. The sound pressure waveform is a short pulse of almost one cycle, and it can be visually understood that high time resolution can be obtained. Although the peak of the spectrum is about 25 kHz, the effective Q value is about 0.8, and the frequency characteristic obtained by the impulse method is almost similar to the tendency of the frequency characteristic shown in FIG.
　図８は駆動電圧に対する音圧の測定結果である。横軸は駆動電圧、縦軸は音圧である。駆動電圧の二乗に比例して音圧が増加していることが確認できる。圧電方式や電磁方式は駆動電圧または駆動電流に比例した音圧出力が得られるが、この点において異なっており、電歪方式に類似の関係となっている。駆動電圧100Vp-pでピークパワーは250W、バースト波内の実効電力は125Wになる。パルス駆動なので例えばduty 1%では1.25Wにまで低くでき、実用的な電力レベルとなる。なお、駆動電圧180Vp-p以上で音圧が飽和しているのは、この実験で用いたパワーアンプの出力が飽和するからである。 FIG. 8 shows the measurement result of the sound pressure with respect to the drive voltage. The horizontal axis is the drive voltage, and the vertical axis is the sound pressure. It can be confirmed that the sound pressure increases in proportion to the square of the drive voltage. The piezoelectric method and the electromagnetic method can obtain a sound pressure output proportional to the driving voltage or driving current, but are different in this respect and have a relationship similar to the electrostriction method. With a driving voltage of 100Vp-p, the peak power is 250W and the effective power in the burst wave is 125W. Since it is a pulse drive, it can be reduced to 1.25W at a duty of 1%, for example, and it becomes a practical power level. The reason why the sound pressure is saturated at a drive voltage of 180 Vp-p or more is that the output of the power amplifier used in this experiment is saturated.
　図９は伝搬特性を示す図であり、横軸は音波源からマイクまでの距離、縦軸は音圧である。図９から、音圧は距離に反比例して拡散減衰していく様子が確認できる。距離3cmで音圧は3Pap-p程度であるので近距離での物体検知に利用できる。例えば複写機やプリンタの用紙重送検知などのアプリケーションに使える。 FIG. 9 is a diagram showing propagation characteristics, where the horizontal axis represents the distance from the sound wave source to the microphone, and the vertical axis represents the sound pressure. From FIG. 9, it can be confirmed that the sound pressure is diffused and attenuated in inverse proportion to the distance. Since the sound pressure is about 3Pap-p at a distance of 3cm, it can be used for object detection at a short distance. For example, it can be used for applications such as copier and printer paper double feed detection.
　図１０は指向特性を示す図であり、横軸は方位角、縦軸は音圧の相対値である。この例の場合、半減全角（音圧が最大となる角度を０℃としたとき、音圧が半減するまでの角度）でおよそ70度（－３５°～３５°）であり、音波の周波数が図６より32kHzであり、折り返し電極であるため送波面の長さが約６mmであることを考慮すると、充分に狭指向性であることがわかる。一般的に、有底筒状のケースの底面に圧電素子を貼り付けて、圧電素子によるベンディング振動を利用した超音波センサでは、周波数が高くなるほど狭指向性が得られることが知られているが、ベンディングのため理想的なピストン音源（音圧放射面から放射される音波の位相および振幅が一様である音源）よりは広指向性となる。本発明の構造によれば、理想的なピストン音源と同様、比較的低周波数（例えば３０～４０ｋＨｚ）で狭指向性が実現できるという知見が得られた。これは、駆動時において、音源となるアルミナ基板及び厚膜導体が振動しないことが寄与しているものと思われる。
《第３の実施形態》
　第３の実施形態では、第１・第２の実施形態で示した音波源とは異なる厚膜導体のパターンの幾つかの例を示す。
　図１１に示す３つの音波源のいずれも、絶縁性基板１１と、この絶縁性基板１１上に形成された、金属材料とガラス成分を含む厚膜導体１３および接続電極１４，１５を備えている。図１１（Ａ）に示す厚膜導体１３は、破線の円で示すように円形領域内にミアンダライン状のパターンを形成している。図１１（Ｂ）に示す厚膜導体１３は、ほぼ正方形領域内にミアンダライン状のパターンを形成している。図１１（Ｃ）に示す厚膜導体１３も全体にほぼ正方形を形成しているが、複数のラインを並列接続している。 FIG. 10 is a diagram showing the directivity, where the horizontal axis represents the azimuth angle and the vertical axis represents the relative value of the sound pressure. In this example, the half angle is about 70 degrees (-35 ° to 35 °) when the angle at which the sound pressure reaches the maximum is 0 ° C. From FIG. 6, it is found that the directivity is sufficiently narrow considering that the frequency is 32 kHz and the length of the transmission surface is about 6 mm because it is a folded electrode. In general, an ultrasonic sensor using a piezoelectric element attached to the bottom surface of a bottomed cylindrical case and utilizing bending vibration by the piezoelectric element is known to obtain a narrow directivity as the frequency increases. Because of bending, it has a wider directivity than an ideal piston sound source (a sound source in which the phase and amplitude of a sound wave radiated from the sound pressure radiation surface is uniform). According to the structure of the present invention, it has been found that narrow directivity can be realized at a relatively low frequency (for example, 30 to 40 kHz) as in the case of an ideal piston sound source. This is considered to be due to the fact that the alumina substrate and the thick film conductor as the sound source do not vibrate during driving.
<< Third Embodiment >>
In the third embodiment, some examples of patterns of thick film conductors different from the sound wave source shown in the first and second embodiments are shown.
Each of the three sound wave sources shown in FIG. 11 includes an insulating substrate 11, a thick film conductor 13 including a metal material and a glass component, and connection electrodes 14 and 15 formed on the insulating substrate 11. . In the thick film conductor 13 shown in FIG. 11A, a meander line pattern is formed in a circular region as indicated by a broken-line circle. The thick film conductor 13 shown in FIG. 11B forms a meander line pattern in a substantially square region. The thick film conductor 13 shown in FIG. 11C also has a substantially square shape as a whole, but a plurality of lines are connected in parallel.
　厚膜導体１３の形成領域が音波の送波面となるので、この厚膜導体１３の形成領域の面積と形状で指向性の制御および設計が可能である。例えば、図１１（Ａ）～（Ｃ）に示されるように、厚膜導体１３の形成領域の面積を増すほど、音波の等位相面が平行となる領域が拡がるので、指向性ビームの幅を狭くできるため、より好ましい。また、厚膜導体１３の形成領域の形状が縦方向と横方向の幅が異なれば、ビームの縦方向の幅と横方向の幅を異ならせることもできる。 Since the formation region of the thick film conductor 13 serves as a sound wave transmission surface, the directivity can be controlled and designed by the area and shape of the formation region of the thick film conductor 13. For example, as shown in FIGS. 11 (A) to 11 (C), as the area of the thick film conductor 13 is increased, the area in which the isophase planes of sound waves are parallel increases, so that the width of the directional beam is increased. Since it can narrow, it is more preferable. Further, if the shape of the region where the thick film conductor 13 is formed has different vertical and horizontal widths, the vertical and horizontal widths of the beam can be made different.
　また、厚膜導体１３は必要な抵抗値、面積、形状に応じてパターンを決定すればよい。厚膜導体１３の膜厚によっても抵抗値が定められるが、膜厚と熱容量は密接に関係するので、高周波の駆動電圧で駆動する場合には、所定の感度が得られる程度に薄くする等、種々調整することが好ましい。なお、本発明の厚膜導体は、アルミナ基板上に、金属材料とガラス成分とを含む導体ペーストを塗布・印刷し焼き付けることによって形成されるので、抵抗値、面積、形状等の調整を容易に行うことができる。 Moreover, the thick film conductor 13 may be determined in accordance with the required resistance value, area, and shape. The resistance value is also determined by the film thickness of the thick film conductor 13, but since the film thickness and the heat capacity are closely related, when driving with a high-frequency driving voltage, the resistance is made thin enough to obtain a predetermined sensitivity. Various adjustments are preferable. The thick film conductor of the present invention is formed by applying, printing and baking a conductor paste containing a metal material and a glass component on an alumina substrate, so that the resistance value, area, shape, etc. can be easily adjusted. It can be carried out.
　このように、本発明によれば、厚膜導体の形状を任意に決定できるので、送波面が自在に設定でき、指向性の制御および設計が容易になる。 Thus, according to the present invention, since the shape of the thick film conductor can be determined arbitrarily, the wave transmission surface can be freely set, and directivity control and design are facilitated.
《第４の実施形態》
　第４の実施形態では、直流電源で音波源を駆動するようにした超音波発生装置の例を示す。図１２は第４の実施形態に係る超音波発生装置２０４の回路図である。この超音波発生装置２０４は、パルス発生回路４１、直流電源４３、MOSFET４２、および音波源１０４で構成されている。この例では、MOSFET４２のソースが接地され、MOSFET４２のドレインと直流電源４３との間に音波源１０４が接続され、MOSFET４２のゲート・ソース間にパルス発生回路４１のパルス電圧が印加されるように構成されている。 << Fourth Embodiment >>
In the fourth embodiment, an example of an ultrasonic generator in which a sound wave source is driven by a DC power source is shown. FIG. 12 is a circuit diagram of the ultrasonic generator 204 according to the fourth embodiment. The ultrasonic generator 204 includes a pulse generation circuit 41, a DC power supply 43, a MOSFET 42, and a sound wave source 104. In this example, the source of the MOSFET 42 is grounded, the sound wave source 104 is connected between the drain of the MOSFET 42 and the DC power supply 43, and the pulse voltage of the pulse generating circuit 41 is applied between the gate and source of the MOSFET 42. Has been.
　図１３は、図１２に示したパルス発生回路４１により発生されるMOSFET４２のゲート信号と音波源１０４から放射される音波の音圧波形（マイクで検出した信号の波形）の例である。図１３の左側の波形はゲート信号、右側の波形は音圧波形である。ゲート信号の１つのパルス幅は１２．５μｓであり、上から１波、２波、４波の例を示している。
　この構成によれば、駆動電流が単極に存在するので、ゲート信号と同じ波数の音圧波形が得られる。 FIG. 13 shows an example of the gate signal of the MOSFET 42 generated by the pulse generation circuit 41 shown in FIG. 12 and the sound pressure waveform of the sound wave radiated from the sound wave source 104 (the waveform of the signal detected by the microphone). The left waveform in FIG. 13 is a gate signal, and the right waveform is a sound pressure waveform. One pulse width of the gate signal is 12.5 μs, and an example of one wave, two waves, and four waves from the top is shown.
According to this configuration, since the drive current exists in a single pole, a sound pressure waveform having the same wave number as the gate signal can be obtained.
《他の実施形態》
　絶縁性基板の厚膜導体面は曲面に形成されていてもよい。この構造により、空気加熱によって発生する空気の圧力波の等位相面が厚膜導体面は曲面に沿って形成される。したがって、絶縁性基板の厚膜導体面の曲面形状を定めることによって音波のビーム形状を制御してもよい。 << Other Embodiments >>
The thick film conductor surface of the insulating substrate may be formed in a curved surface. With this structure, the equiphase surface of the pressure wave of air generated by air heating is formed along the curved surface of the thick film conductor surface. Therefore, the beam shape of the sound wave may be controlled by determining the curved surface shape of the thick film conductor surface of the insulating substrate.
　また、例えば前記厚膜導体のパターンを複数のパターンの集合体パターンで構成し、バースト波電圧発生回路が複数の厚膜導体パターンに対してそれぞれ異なった位相のバースト波電圧を印加するように構成してもよい。そのことによって、基板に対する超音波の指向方向を制御することもできる。 Further, for example, the thick film conductor pattern is constituted by an aggregate pattern of a plurality of patterns, and the burst wave voltage generating circuit applies burst wave voltages having different phases to the plurality of thick film conductor patterns. May be. Thereby, the directivity direction of the ultrasonic wave with respect to the substrate can be controlled.
　また、本発明の厚膜導体は金属材料とガラス成分とを含む構造からなるため、発熱部材としての機能を果たすだけではなく、電極としても十分に機能し得る。このため、接続電極は必ずしも必要ではない。 Further, since the thick film conductor of the present invention has a structure including a metal material and a glass component, it can function not only as a heating member but also as an electrode. For this reason, a connection electrode is not necessarily required.
１１…絶縁性基板
１３…厚膜導体
１４，１５…接続電極
２１…バースト波信号発生回路
２２…電力増幅回路
３１…マイク
３２…プリアンプ
３３…バンドパスフィルタ
３４…オシロスコープ
４１…パルス発生回路
１０１，１０２，１０４…音波源
２０１，２０４…超音波発生装置
３０１…特性測定装置 DESCRIPTION OF SYMBOLS 11 ... Insulating board | substrate 13 ... Thick film conductors 14 and 15 ... Connection electrode 21 ... Burst wave signal generation circuit 22 ... Power amplification circuit 31 ... Microphone 32 ... Preamplifier 33 ... Band pass filter 34 ... Oscilloscope 41 ... Pulse generation circuits 101, 102 , 104 ... sound wave sources 201, 204 ... ultrasonic wave generator 301 ... characteristic measuring device

Claims (3)

  1. 　絶縁性基板と、前記絶縁性基板上に形成された、金属材料とガラス成分を含む厚膜導体とで構成された音波源。 An acoustic source composed of an insulating substrate and a thick film conductor containing a metal material and a glass component formed on the insulating substrate.
  2. 　前記厚膜導体は、前記絶縁性基板上に、金属材料とガラス成分とを含む導体ペーストを塗布・印刷し焼き付けることによって形成された、請求項１に記載の音波源。 2. The acoustic wave source according to claim 1, wherein the thick film conductor is formed by applying, printing, and baking a conductor paste containing a metal material and a glass component on the insulating substrate.
  3. 　絶縁性基板と、前記絶縁性基板上に形成された、金属材料とガラス成分を含む厚膜導体とで構成された音波源と、前記厚膜導体に印加するバースト波電圧を発生するバースト波電圧発生回路と、を備えた超音波発生装置。 A sound wave source composed of an insulating substrate, a metal film and a thick film conductor containing a glass component formed on the insulating substrate, and a burst wave voltage for generating a burst wave voltage applied to the thick film conductor And an ultrasonic generator.
PCT/JP2011/063765 2010-08-10 2011-06-16 Soundwave source and ultrasound generation device WO2012020600A1 (en)

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